Infectious diseases kill more people worldwide each year than any other single cause. Minimizing infections caused by pathogenic microorganisms is a great concern in many fields, particularly in medical devices, drugs, hospital surfaces/furniture, dental restoration and surgery equipment, healthcare products and hygienic applications, water purification systems, air filters, textiles, food packaging and storage, industrial or domestic appliances, aeronautics, etc. Particularly in hospitals, great efforts and significant costs are incurred in the fight against infections.
Infections are produced by touching, eating, drinking, or breathing something that contains a pathogen. Generally, these infections are combated with antimicrobial agents that target the pathogen. Particularly problematic, however, are the microorganisms that can rapidly and easily mutate their genes to become resistant to these agents, making their elimination difficult. For instance, Staphylococcus aureus (S. aureus) commonly colonizes on human skin and in mucosa without causing severe problems, but if the bacteria enter the body, illnesses that range from mild to life-threatening can develop, including skin and wound infections, infected eczema, abscess infections, heart valve infections or endocarditis, pneumonia, and bloodstream infections or bacteraemia. Some S. aureus are resistant to methicillin and other β-lactam antibiotics—methicillin-resistant S. aureus (MRSA)—and require alternative types of antibiotics to treat them. Moreover, the spore-forming Clostridium difficile (C. difficile), an intestinal superbug causing symptoms ranging from diarrhea to life-threatening inflammation of the colon, is the most common bacterial infection acquired in hospitals.
Given these health hazards, considerable research effort is being devoted to creating advanced photoreactive materials that can promote, for example, processes such as the photodecomposition of organic and inorganic contaminants (Borgarello et al., Disposal of hydrogen sulfide: conventional and photochemical methods. In M. Schiavello, Ed., Photocatalysis and Environment, p. 567-581, Kluwer Academic Publishers, Dordrecht (1988); Brinkley et al., Journal of Physical Chemistry, 102, 7596-7605 (1998); Fox, Photocatalytic oxidation of organic substrates. In M. Schiavello, Ed., Photocatalysis and Environment, p. 445-467, Kluwer Academic Publishers, Dordrecht (1988); Pelizzetti et al., Photodegradation of organic pollutants in aquatic systems catalyzed by semiconductors, In M. Schiavello, Ed., Photocatalysis and Environment, p. 469-497, Kluwer Academic Publishers, Dordrecht (1988); Serpone et al., Photoreduction and photodegradation of inorganic pollutants: I. Cyanides. In M. Schiavello, Ed., Photocatalysis and Environment, p. 499-526, Kluwer Academic Publishers, Dordrecht (1988a, 1988b)), photosynthesis of organic compounds from carbon dioxide and other inorganic substrates (Anpo et al., Journal of Physical Chemistry, 101, 2632-2636 (1997); Kanemoto et al., Journal of the Chemical Society, Faraday Transactions, 92, 2401-2411 (1996)), photodecomposition of water to hydrogen and oxygen (Lauermann et al., Journal of Electroanalytical Chemistry, 228, 45-55 (1987)), and photoreduction of dinitrogen to ammonia (Augugliaro and Palmisano, Reduction of dinitrogen to ammonia in irradiated heterogeneous systems. In M. Schiavello, Ed., Photocatalysis and Environment, p. 425-444. Kluwer Academic Publishers, Dordrecht (1988)). The role of semiconducting materials as catalysts of redox reactions in natural environments and engineered systems designed to degrade hazardous chemicals is also being increasingly recognized (Schoonen et al., Journal of Geochemical Exploration, 62, 201-215 (1998); Selli et al. 1996; Stumm and Morgan 1995; Sulzberger, Photoredox reactions at hydrous metal oxide surfaces: A surface coordination chemistry approach. In W. Stumm, Ed., Aquatic Chemical Kinetics. Wiley Interscience, New York (1990)).
Despite previous efforts, there continues to be a need to provide photocatalytic composites capable of creating a light-activated antimicrobial film and various other uses.